1. Field of the Invention
This invention relates to a facsimile apparatus having transmitting and receiving means for transmitting and receiving a long training sequence or a short training sequence as the training signal of a modem at the start of a data information transmission and reception and this invention also relates to a training sequence changeover method for use in the facsimile apparatus.
2. Description of the Prior Art
When transmitting an error retransmission frame or a TCF signal and an image block with an apparatus of this type, conventionally the arrangement is such that the same training signal is transmitted. For example, if transmission in a long training sequence is possible at the start of communication, then the training sequence when transmitting an image block and an error retransmission frame or TCF signal also is the same long training sequence.
However, since the operation is such that the same training sequence is transmitted as a training signal in case of the image block and error transmission frame or TCF signal in the above-described example of the prior art, the following drawbacks are encountered:
(1) When a transmission code that requires about 1393 ms is used for the training sequence, as in a modem in accordance with CCITT V.33, communication time is prolonged.
(2) When the error retransmission frame and image block are transmitted in the short training sequence, errors easily occur in the image block and, hence, an error retransmission procedure is required. Moreover, if the error retransmission frame is retransmitted, errors tend to occur in the short training sequence and a longer communication time is required.
(3) Even if an attempt is made to use a short training sequence the same as that of the image block, there is no initial tap value of the modem necessary for the short training sequence. As a consequence, the TCF signal cannot be transmitted.